STOCK VET VOICE
More to it than just “drenching for worms”
Weighing youngstock regularly gives the level of detail required for a targeted drenching programme.
Words by: Lisa Whitfield
Cooperia oncophora
Cooperia inhabits the small intestine. orms are a significant risk Numbers peak on pasture in autumn, and for stock kept at pasture. it is most likely to affect youngstock at The risk is greatest for this stage, during their first year. Cooperia young stock, who doesn’t like cold weather so doesn’t persist need to develop immunity to well between autumn and spring worms in order to be able to when there is a good winter in clear themselves of parasites. between. Cattle typically develop The full development of immunity to this worm by one immunity to important year old. species of worms takes 18 Gastrointestinal disease from to 20 months in cattle. In Cooperia infestation is frequently the meantime there is lingering on farms which practice exclusive Lisa Whitfield susceptibility to the development reliance on single-action macrocyclic of production-limiting disease if lactone pour-on drenches for their good management practices are not put in calves. There is widespread resistance of place and followed. Cooperia to macrocyclic lactone drenches. We are lucky to have only a small number of worms which we need to Trichostrongylus species manage in cattle. Common worms which Three Trichostrongylus species can affect you need to be aware of are: Cooperia cattle in New Zealand - T. axei, T, vitrinus oncophora, Trichostrogyle spp., Ostertagia and T. colubriformis. These worms can ostertagi, and Dictyocaulus viviparus inhabit both the abomasum and the (lungworm). small intestine of their hosts. Immunity
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to Trichostrongylus does not develop until young stock are about 18 months old. Larvae are tolerant to the cold and numbers peak on pasture in spring, so immunity to these worms follows this peak of exposure.
Ostertagia ostertagi This is considered the most significant worm of cattle in NZ. Ostertagia inhabits the abomasum and has the potential to cause significant damage to the lining of this organ. Larval numbers peak in autumn so disease is often seen at this time. Larvae also become dormant in the lining of the abomasum over winter, so disease can also occur the following spring and summer if good immunity has not been developed. There is low efficacy of levamisole and benzimidazole drenches against Ostertagia. On most farms, macrocyclic lactones are effective in controlling Ostertagia, however, resistance to macrocyclic lactone drenches has been found in New Zealand and this should be of concern to all cattle farmers.
Dairy Exporter | www.nzfarmlife.co.nz | December 2021
